The present invention relates to packaging and more particularly to tamper-evident thermoformed packaging.
Thermoformed packaging is used in a wide variety of application. The design and construction of thermoformed packaging typically varies from application to application. One common application for thermoformed packaging is food packaging. For example, fruits and vegetables are now commonly sold in containers made from thermoformed parts. Although food packages may vary in design and construction, one type of common food package includes a thermoformed base and a thermoformed lid that can be closed to cooperatively define an article-receiving space. In some applications, the base and lid are formed from a single portion of thermoplastic material and are joined together along a living hinge. In other applications, the base and lid are separately formed.
The base and lid can be secured together using a variety of different options. For example, the base and lid can be permanently sealed (e.g. welded) together to make it difficult to open and therefore tamper with the content of the package. However, permanently sealed packaging has a number of disadvantages. For example, permanently sealing the package can increase the cost of packaging because it may require the use of relatively expensive sealing equipment (e.g. a welder). Further, consumers have increasingly expressed resistance to the use of permanently sealed thermoformed packaging. Permanently sealed packages can be difficult to open, thereby providing a source of frustration for consumers. As a result of these (and perhaps other) disadvantages, there has been an effort to develop alternative packaging constructions that are not welded or otherwise permanently sealed. Some alternative constructions currently in use include a base and a lid that are snap-fitted together, and can therefore be relatively easily opened and closed simply by lifting the lid away from the base with enough force to overcome the snap-fit engagement.
In some applications, it can be desirable to provide a mechanism that allows a consumer to visually determine whether or not a package has been opened or otherwise tampered with. In packages that rely on snap-fit engagement between the lid and base, it is not uncommon to provide a construction in which a portion of the package must be bent or removed to open the lid. The bent portion or the absence of a removed portion provides a visual indication that the package has been opened or otherwise tampered with. For example, in some conventional packages of this type, the base includes a peripheral rail that surrounds and is closely aligned with the peripheral edge of the lid. The rail prevents easy access to the edge of the lid and thereby makes it difficult to remove the lid from the base. To obtain access to the edge of the lid, a portion of the base containing a section of the rail is capable of being folded down away from the edge of the lid. In this type of container, the movable portion of the base is often joined to the remainder of the base along a hinge disposed at its inner-most edge. In use, the movable portion is folded down along the hinge to gain access to the edge of the lid so that the edge of the lid can be gripped and used to lift the lid away from the base. It can be difficult to recognize when packages of this type have been tampered with. Depending on how far the movable portion is moved, it may not provide the container with sufficient visual discontinuity. Further, the problem can be compounded when, after the movable portion has been bent down, the shape memory of the material forming the hinge attempts to return the hinge to its original shape, thereby pulling the movable portion back into closer alignment with the peripheral edge of the lid.